Over the entire history of man, the treatment of wounds has occupied pre-eminent importance for obvious reasons, yet remarkably little is understood about the mechanics of healing a wound. Many centuries after the recorded history of medicine was first begun, wound dressings still in use have run the gamut of materials and medicaments including synthetic and natural fibers for pads and bandages, and poultices of leaves, crushed seeds, clays and muds of various types, etc. and mixtures of the foregoing. It is only in the very recent past that any significant effort has been devoted to how best select a wound dressing for a particular wound. It is only still more recently that, galvanized by the need for efficient and speedy patient-care demanded by present day health care organizations, much attention has been devoted how better to deliver a wound dressing quickly, effectively and aseptically to the wound site, than a conventional adhesive wound dressing. These efforts have evolved into the use of "adhesive film wound dressings", which are constructed for a particular application and are appropriately sized so as to permit the use of the dressings on a relatively large area of human skin.
By the term "adhesive film wound dressing" we refer to one comprising a laminar backing sheet or strip of oxygen-permeable and water vapor-permeable synthetic resinous thin film, less than 2 mils thick, which is coated over at least a portion of one surface with a biocompatible, pressure-sensitive adhesive for directly adhering the dressing over a wound surrounded by skin. Such wound dressings necessarily provide a barrier against infectious microorganisms and are typically essentially impervious to liquid water and wound exudate which is confined by the dressing when it is adhesively secured over a wound.
An adhesive film wound dressing may include on its adhesive-coated side, an absorbent pad of porous material to be placed around, or in contact with the wound. Such pad-including dressings are referred to as "island dressings". All reference to a "wound dressing" or "dressing" refers to an adhesive film wound dressing which may also be an island dresing. A dressing without an island is referred to as a "film only" dressing.
The proportion of the surface of the film coated with adhesive is not narrowly critical, but the wound dressing of this invention is of the type in which the adhesive coats the major portion of the area to be placed in contact with the skin, and more preferably, substantially the entire surface of the dressing to be in contact with the skin.
Since the adhesive is pre-applied to the dressing, the coated surface must be protected while the dressing is packaged, shipped and sorted prior to being used. Just prior to applying the dressing, the protection must be removed and the dressing applied aseptically to the wound without letting the adhesive surface of the dressing stick to any other surface (including the fingers of the hands applying the dressing) than over the wound area.
Smoothly applying the adhesive dressing over the Wound, without wrinking the dressing, and with a minimum of fuss and bother, is of crucial importance if the dressing is to gain acceptance among persons expected most frequently to apply it, namely those in the health care field, such as nurses and physicians.
Numerous dressings have been disclosed which purport to satisfy the foregoing criteria but have fallen short of their promise for one reason or another. A recent, commercially available dressing is disclosed in U.S. Pat. No. 4,513,739 to Johns (class 128/subclass 156) and has met with qualified success; a less recent one is disclosed in U.S. Pat. No. 3,018,881 (class 206/subclass 441). Both emphasize the need to provide an easy delivery system for delivering the adhesively-coated film to the wound site; and each focuses the critical importance of removing the release sheets, which provide a protective shield, in such a way as to make positioning the dressing on the wound a simple and expeditious task.
It is self-evident that the dressing must be placed over the wound without having one portion of the adhesive surface contact another, because the adhered portions cannot generally thereafter be separated. It is also self-evident that the release sheets cannot be pulled off the adhesive surface, in toto, before the dressing is placed over the wound, because one would then have lost manual control of the dressing, and if such control was retained, the dressing could not be applied aseptically. Therefore, it is essential that the release sheets on the adhesively coated film be so constructed that they not only provide aseptic protection for the coated front surface of the film, but also that, when pulled upon, they do not come off in toto, but only partially, thus providing the nurse, or other person, a chance to position and adhere the dressing precisely where it is to be located over the wound.
To this end, the '739 and '881 references each introduces an element which provides such a chance in the form of a release-retarding means along one edge or a pair of opposed edges of the dressing, so that a greater force is required to separate the release sheet at the edge than that required to separate the sheet from the remainder of the contacting area. The '881 patent simply discloses that flap 32 and panel 14 of the bandage are peelably or strippably adhered to the ends of portions 26 and 28 respectively, but the '739 patent specifies numerous release-retarding means for providing the greater peel strength at the edges of the dressing.
Among the release-retarding means suggested in the '739 patent are (1) a strip of flexible tape attached to the second or rear face of the backing sheet to provide a heat sink for an infra-red heat source used to increase the adhesive strength at the edges; (2) a strip of backing sheet having a thickness greater than that of the remainder of the backing sheet; (3) a strip of adhesive on the front face of the backing sheet to provide greater tenacity than the biocompatible adhesive covering the rest of the sheet; inter alia.
The extreme simplicity of the design and construction of the basic embodiments of our wound dressing requires the use of only two components, namely the adhesively coated film, and a release layer comprising two release sheets. An additional element, namely an absorbent pad may be included, if an island dressing is desired. The simple design eschews the introduction of release-retarding means suggested by the prior art, yet provides an equivalent function in the form of a interrupting line of incisions or perforations which provide a "temporary stop" in only one, or both release sheets in first and second embodiments respectively, during the removal of the sheets, prior to application of the dressing. The temporary stop is provided without introducing an additional structural element. We simply provide the interrupting line of incisions or perforations pierced through at least one release sheet, the piercing being effected in a direction from the outer surface of the release sheet to its inner surface which is in contact with the adhesive surface of the film, referred to as the "front" surface.
Moreover, we have found that the location of the "temporary stop" as it is provided in our release sheet(s) at least 1.25 cm from a side-edge, is critical if the dressing is to be applied with slight pressure in a direction normal to the surface of the skin of a patient in the supine position, the pressure being exerted downwardly upon the wound, simultaneously with a pulling action which provides tension in a lateral plane. Locations suggested by the '739 and '881 references, of their release-retarding means along one or both edges of their films, simply fail to provide the necessary distribution of tensile forces over the surface area of the dressing, for smoothly tensioning the dressing during the final stages of the application procedure. The temporary stop provided by the interrupting line of incisions or perforations in spaced-apart relation from the edges of the film, so as to provide relatively wide, opposed side-margins to distribute tensile forces over the film, allows one to do so.